PRACTICALITY OF CRANIOSPINALIRRADIATION

CSI - CRANIO-SPINAL IRRADIATION
3/15/2023 1
DR KANHU CHARAN PATRO
MD,DNB(Radiation Oncology),MBA,FICRO,FAROI(USA),PDCR,CEPC
HOD,RADIATION ONCOLOGY
Mahatma Gandhi Cancer Hospital And Research Institute, Visakhapatnam
drkcpatro@gmail.com /M- +91-9160470564

What is this?
• Total neuroaxis radiation
• Brain and spine
• CSF spaces
– Brain
– Spine
– Cranial nerves
– Spinal nerve roots

Why is this?
• CSF spread
– Medulloblastoma
– Germ cell tumors
– Anaplastic ependymoma
– PNETs
– Pineoblastomas
– CNS Neuroaxis Mets

• Medulloblastomas are the most common
malignant brain tumour of childhood.
• They most commonly present as midline masses in
the roof of the 4th ventricle with associated mass
effect and hydrocephalus.
• Treatment typically consists of surgical resection,
radiation therapy, and chemotherapy, with the
prognosis strongly influenced by surgical resection,
the presence of CSF metastases at the time of
diagnosis
• 2021 update of the WHO classification of CNS
tumours, which recognizes four molecular subgroups
• The radiographic features are strongly influenced by
the histological type and molecular subtype of the
tumour
Introduction

Morphological risk stratification

Surgical principle
1. However, routine pre-operative ventriculo-peritoneal (VP) shunt should
generally be avoided[ as definitive surgical resection readily relieves the
obstructionby opening the cerebrospinal fluid (CSF) pathways.
2. Besides the possible morbidity associated with a VP shunt, it can lead to
‘reverse herniation’ of the superior vermis into the quadrigeminal cistern and
occasionally seeding of the tumor into the peritoneal cavity.
3. Occasionally, CSF diversion may be deemed necessary for symptomatic relief
if there is anticipated delay in definitive surgery.
4. Such diversion is best achieved using either an external ventricular drainage
(EVD) or an endoscopic third ventriculostomy ((ETV)
5. If CSF diversion is not being considered, medical decompressive therapy is
recommended in the pre-operative period.
6. The steroid of choice is dexamethasone administered in a loading dose of
0.5-1 mg/kg intravenously (with the maximum dose being 10 mg
7. Complete surgical removal should be tried.

Concurrent Chemotherapy
1. Concurrent weekly vincristine (1.5mg/m2) given as an
intravenous bolus throughout the course of RT is
recommended (as in the original Packer’s regimen) for
children with standard risk disease being treated with
reduced dose CSI.
2. For children with high risk medulloblastoma, the use of
daily concurrent carboplatin (35mg/m2) as a short
intravenous infusion throughout the course of RT has
demonstrated very promising outcomes with
manageable acute toxicity and it is left to the discretion
of the treating physician whether to employ concurrent
carboplatin in routine clinical practice

Radiation principle
1. Whole neuroaxis radiation followed by tumor bed boost
is the standard
2. Children below 3 years need chemo till 3 years and
need radiation after that

TRAGET DELINEATION
• Craniospinal
– Whole brain
• Cribriform plate
• Skull base
• Cranial nerves
• Foramina
– Spine
• Entire subarachnoid space to
encompass the extensions along the
nerve roots laterally
Since the entire CSF space is at risk
of disease dissemination, the entire
arachnoid space is defined as the
CTV

IMAGING PROTOCOL
• From vertex to mid thigh
• CT
• MR spine T2
• MR brain FIESTA/ T1
FSPGR/T2
• 1-3mm slice

The missing target
cribriform plate
Ensure that the cribriform plate (suggested
CT window/ level: 3000/400),

The missing target
THE cribriform plate
1. Cribriform plate is a thin horizontal
plate of ethmoid bone which is
bounded laterally by vertical
lateral lamella
2. Includes brain with entire frontal lobe
and cribriform plate.

The missing target
Lower Part Of Temporal Lobe

The missing target
foramina
1. Cranial nerve roots with their individual ‘dural
sheaths and spinal nerve roots as they emerge
from neural foramen within the high-dose
radiotherapy region
2. The observation on MRI of CSF flow beyond the
inner table of the skull into cranial nerve
foramina and canals raises
3. The issue of accurate delineation of all CSF
spaces as CTV for CSI
4. The SIOPE approach recommends a 5-mm
margin inferior to the cribriform plate and 10-
mm below the rest of the skull base whereas
5. Children’s Oncology Group (COG) advises a
uniform margin of 5 mm below the skull base

The dural cuff of cranial nerves

Cochlea sparing
• Attempts to spare the cochlea by
excluding CSF within the internal
auditory canal should be
avoided.

Pituitary sparing
The whole pituitary fossa
should be included in
CSI but not in boost
planning

CTV spinal
• CTV spinal including the entire
arachnoid space with nerve roots

Determination of end of
thecal sac

Vertebra
The parts of the vertebrae bearing growing plates (the body of the vertebra, the
posterior element and facet joints; but not the lateral elements and transverse
processes) should be enclosed to a uniform dose

The PTV margin
The PTV margin should be
based on departmental data.
Most institutions add a 3–5
mm margin to CTV cranial
5–8 mm margin to CTV
spinal.

Timing of radiation
• Adjuvant RT should ideally begin as early as is
feasible (allowing 2-3 weeks for post-operative
recovery and neuraxial staging), preferably within
4-weeks, but within 6-weeks of surgery.
• The overall treatment time of fractionated course of
RT should preferably not exceed 50 days, but not 8
weeks
• Treatment interruptions during RT are undesirable
and should be avoided as far as practical

Pre RT investigations
• Full MRI brain and spine till mid thigh
• CSF study for malignant cells

Imaging in post op
1. It is recommended that post-operative MRI of the
brain be acquired immediately (within 24-48 hours
of surgical resection) to accurately identify the
extent of resection and quantify the status of the
residual disease.
2. However, whenever immediate post-operative
neuro-imaging has not been obtained, it is
recommended to wait for 2-3 weeks (but no later
than 4-weeks) to allow resolution of post-operative
changes (blood products and surgical debris) for
better delineation and characterization of the tumor
bed.
3. If screening spinal imaging had not been done
pre-operatively, the same should be acquired
post-operatively for an accurate spinal staging.
4. Once again, it is recommended to wait for 2-3
weeks after surgery for acquiring the spinal MRI to
reduce the chance of erroneous interpretation
consequent to post-operative enhancement of
spinal leptomeninges

CSF study?
• It is recommended to test the CSF for malignant cell
cytology via. lumbar puncture as a part of the
post-operative staging work-up
• This should be performed at least 2-3 weeks after
surgery to avoid false positivity.
• CSF obtained via a ventricular tap at the time of
surgery is not considered appropriate for neuraxial
staging

MRI AND CSF STUDY
which is first?
• Do CSF study after MRI
• Because LP site gives artifact Wrong interpretation of drop mets
• If CSF done first wait for 1/2 week
• Ask for sagittal MRI slice proper visualization

Supine or prone?
• Supine – Subject(patient) comfort
• Prone – Physician comfort

2D/3D/ARC?
• Any
– 2D- Crude
– 3D- Better
– ARC- Wow

Why so special?
• Total length
• Field size less – 40cm x 40 cm
• Roughly 80-100 cm
• Junction
• Lateral cranial and anterior in
spinal

What is our aim?
• Homogenous dose to target
• Less dose to OAR
• Less integral dose

Kids
Those requiring anesthesia

SEE THE GAP
BETWEEN MASK AND VERTEX
MASK AND SHOULDER

Alignment of the thoracic & lumbar spine parallel to
the couch
Thermocol wedge

The portals
1. Whole Brain: Two parallel opposed lateral
field.
2. UPPER Spine: Direct Posterior field
3. LOWEER Spine: Direct Posterior field

How to fix the junction?
• Playing with
– Gantry
– Couch
– Collimation
• Junction shift or feathering
– Daily
– weekly

Sagittal junction
Cranial and spinal

Beam overlap
collimator correction

How to fix the junction coronal?

Cranial and spinal
CAN I USE HALF BEAM BLOCK?

Cranial and spinal
Half beam block

Half beam block

Spinal and spinal field
how much gap?

Beam overlap spinal – spinal
Gantry correction

GANTRY ANGLE WITH COUCH
ROTATION

How many junction required?
• Each beam 40 cm
• Keep 3 cm for junction shift
• 37cm
• If length of treatment
– 40cm-combination of two half beams [rare]
– 74 cm – one junction
– More than 74 cm-2 junctions
• Combination of half beam and divergent
beam
• Or all divergent beam

Make junction marks
CJN1, CJN2,CJN3
SJN1, SJN2,SJN3

Where to put cranio-spinal
junction
• Ensure that spinal field
should not exit through
oral cavity and thyroid if
possible
• At least clearance from
shoulder is required in
lateral cranial field

Where to keep spinal-spinal
junction

The BLUE LINE AND RED LINE
CONCEPT

EVERYDAY SETUP CHECK LIST
1. POSITION
2. ALLIGNMENT LASER
3. GAP BETWEEN MASK AND HEAD
4. ANY SHOULDER GAP
5. LEG AND FEET POSITION
6. LOWER BORADER OF CRANIAL AND UPPER BORDER OF SPINAL
DATE RL CRANIAL LL CRANIAL
GANTRY COLL. COUCH SSD GANTRY COLL. COUCH SSD
90 10 10 93 270 350 350 93
DAY1
DAY 2
DAY 3
DAY 4
DAY 5
DAY 6
DAY 7

EVERYDAY SETUP CHECK LIST
1. POSITION
2. ALLIGNMENT LASER
3. GAP BETWEEN MASK AND HEAD
4. ANY SHOULDER GAP
5. LEG AND FEET POSITION
6. LOWER BORADER OF LOWER SPINAL FIELD AND UPPER BORDER OF LOWER SPINAL FIELD
DATE UPPER SPINE FIELD LOWER SPINE FIELD
GANTRY COLL. COUCH SSD GANTRY COLL. COUCH SSD
0 0 0 95 345 0 90 94
DAY1
DAY 2
DAY 3
DAY 4
DAY 5
DAY 6
DAY 7

The extended SSD
1. Advantage
• Single spinal field and circumventing the
issue of junction between two spinal fields
2. Disadvantage
• Higher percentage depth dose and greater
penumbra results in higher mean doses to
all anterior normal structures,(mandible,
esophagus, liver, lungs, heart, gonads and
thyroid gland)

What dose?
• Total dose
– Whole neuroaxis dose + Boost dose
• Whole neuroaxis + Boost dose
– High risk
• CSI-35Gy/21#
• Boost -19.8Gy/11#
• Total -54.8Gy/33#
– Low risk
• CSI (23.4Gy/13#)
• Boost (30.6Gy/17#)
• Total - 54Gy/ 30#

What dose if leptomemningeal mets?
• Total dose
– Whole neuroaxis dose + Boost dose + brain and nodular
extra dose
• Whole neuroaxis + Boost dose
– High risk
• CSI-
– 39.6-40Gy/22-24#
• Boost
– -14.4Gy /8 #
• Focal nodular metastatic deposits brain
and spine
– 5.4-9Gy /3-5 #

Medications?
• Antiemetics
– Ondansetron
• Steroids -CAUTION
• Antiepileptics as per need

Investigations?
• Weekly CBP- Complete blood count
• [Hb/WBC/TPL]

If low blood count?
• Keep the boost plan ready and start boost
plan stop CSI plan, if neutropenia and
thrombocytopenia

How to handle myelosuppression?
• It is preferable to avoid using prophylactic growth
factors during CSI, unless deemed necessary.
• However, growth factors may need to be
administered to maintain an absolute neutrophil
count >1 × 109/L to prevent unnecessary treatment
interruptions.
• Similarly, platelet transfusions are not
recommended routinely for mild thrombocytopenia,
but should be reserved for grade 3 or worse
thrombocytopenia to maintain a platelet count >50 ×
109/L during CSI

Using of steroid during treatment?
• The routine use of steroids (dexamethasone or
prednisone) is strongly discouraged unless
necessary (e.g. features of raised intra-cranial
pressure or therapy-induced intractable delayed
nausea/vomiting)

Concurrent chemo during radiotherapy?
• Concurrent weekly vincristine (1.5mg/m2) given
as an intravenous bolus throughout the course of RT
is recommended (as in the original Packer’s
regimen) for children with standard risk disease
being treated with reduced dose CSI.
• For children with high risk medulloblastoma, the use
of daily concurrent carboplatin (35mg/m2) as a
short intravenous infusion throughout the course of
RT has demonstrated very promising outcomes with
manageable acute toxicity and it is left to the
discretion of the treating physician whether to
employ concurrent carboplatin in routine clinical
practice

Boost
• Local
• Whole posterior fossa

SUMMARY
1. CSI is needed in medulloblastoma
2. You can plan with 2D/3D
3. Daily set up needed
4. Weekly junction shift is fine
5. If possible, plan with VMAT/TOMO
6. In TOMO no junction required if treatment
length 130cm
7. If not sure about molecular profile plan with
standard dose
8. Still posterior fossa boost is standard
9. In CBCT verification with 2 /3points required
10. Problem comes with longitudinal as you may
get longitudinal{Y} shifts every iso
11. Move only one site longitudinal {Y}
12. No need to move all sites longitudinal
movements {Y}
13. Only change lateral {x} and vertical{z}
14. Plan concurrent chemo
15. Send for adjutant chemo

Follow UP?
• Follow-up assessment should include a detailed physical
examination including evaluation of the neurological status and a
pro-active surveillance of the treatment-related late effects
– 3-monthly for the first 2-years,
– 6 monthly till 5-years,
– Annually thereafter
• Contrast-enhanced MRI of the brain and spine is recommended at
6-12 weeks after completion of all therapy to serve as a baseline for
future comparison
• Routine imaging surveillance is not recommended, but should be
ordered only if neurologic worsening occurs, recurrence/
progression of disease is suspected,

PRACTICALITY OF CRANIOSPINALIRRADIATION

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